In recent years, to increase recording density and capacity of a disk device or decrease the size thereof, perpendicular magnetic recording mechanisms have been proposed. A recording head having such a mechanism includes a main magnetic pole, which generates a perpendicular direction magnetic field, a write shield magnetic pole, which is located on a trailing side of the main magnetic pole across a write gap, and a coil, which causes a magnetic flux to flow through the main magnetic pole. Additionally, a high-frequency assisted head has been proposed, which includes a high-frequency oscillator, such as a spin-torque oscillator, in the write gap between the write shield magnetic pole and the main magnetic pole, and allows electric current to flow to the spin-torque oscillator via the main magnetic pole and the write shield magnetic pole.
Moreover, a recording head having a plurality of spin-torque oscillators in the write gap has been proposed. Each of the spin-torque oscillators has the same stacked film structure. In such a structure, electric current applied to the film surface causes the spin-torque oscillators to oscillate concurrently. In recent years, to improve recording density, a shingled recording method has been proposed, which sequentially writes recording tracks in an overlapping manner with part of the previously written recording track. As mentioned above, in a recording head including a plurality of spin-torque oscillators, the spin-torque oscillators concurrently oscillate. However, such a recording head is unlikely to be compatible with the shingled recording method.
Moreover, a recording head in which an electrode terminal for energization and a plurality of insulating layers are provided inside each spin-torque oscillator has been proposed. In such a spin-torque oscillator, an interval between a main magnetic pole and a write shield magnetic pole (i.e., a write gap) would become wider due to the electrode terminal and the insulating layers. To improve linear recording density, widening of the write gap is undesirable.